The effect of electron beam irradiation of stoichiometric hydroxyapatite (Ca10(PO4)6(OH)2, HAP) is investigated using electron energy loss spectroscopy (EELS) in the scanning transmission electron microscope (STEM) mode equipped with a LaB6 gun. Initial irradiation at 160 A cm−2 dose rate shows no modification of the low loss spectra. No difference of mass loss for Ca, O and P is observed for two different probe diameters: 4 nm (dose rate = 160 A cm−2) and 24 nm (dose rate = 70 A cm−2). Furthermore no formation of CaO is observed for both experimental conditions. It is proposed that the low values of both electron dose rates and doses (from 350 to 2400 C cm−2) avoid mass loss. At the higher dose rate obtained with a field emission gun (FEG), transformations are observed for the lowloss signal as well as for the Ca, P and O signals. These results might be very useful for the future studies of apatite particles at the nanoscale.

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